Motion translating mechanism for toothbrush power handle



Oct. 6, 1964 G. HOVHANESIAN ETAL MOTION TRANSLATING MECHANISM FORTOOTHBRUSH POWER HANDLE Filed May 31, 1962 2 Sheets-Sheet l The/'r' A twww Oct. 6, 1964 3,152,272

MOTION TRANSLATING MECHANISM FOR TOOTHBRUSHOPOWER HANDLE G. HOVHANESIANETAL 2 Sheets-Sheet 2 Filed May 3l, 1962 United States Patent C3,152,272 lt/itiliiilsl TRANSLATNG MECHANESM FR TUTHERUSH Ptit/'VERHANBUE Garabed liilovhanesian, Westhoro, and Daniels lli. ltiisli,

Framingham, Mass., assignors to Generai Electric Coinpany, a corporationof New York Filled May Si, i962, Ser. No. 193,855 5 Qllairns. (Cl.Sith-S3) rlhis invention relates to amotorized handle for driving atoothbrush, and more specifically to an improved motion translatingmechanism for use in such power handles.

In a copending application of Edgar A. Phaneuf and Hans Springer, SerialNo. 198,883, tiled May 31, 1962, and assigned to the same assignee asthe present invention, lthere is disclosed an electrically operatedtoothbrush including a motorized handle for holding and driving atoothbrush. The handle contains an internal mechanism for converting themotor rotational output into straight line reciprocation of a holdingmember adapted to hold a toothbrush handle. More specifically, therotational output is, through gearing, changed to circular motion of adriving pin which, in turn, cooperates with a slot in the holding memberto reciprocate the member. lt is, of course, desirable that suchmechanism operate reliably and ediciently.

Accordingly, it is a primary object oi the invention to provide a powerhandle with an improved motion translating mechanism which willcooperate with a toothbrush motor driving pin and other elements toreliably and efficiently convert arcuate movement of the pin intostraight line reciprocation of a toothbrush holder.

Brietiy stated, the improved motion translating and holding member ofthe invention is used in a motorized handle which includes a tubularcasing and a motor positioned therein. A driving pin is mounted withinthe casing in a direction substantially perpendicular to the casinglongitudinal axis. The motor is connected to move the pin in a circularpath in a direction transverse to the pin axis. The motion translatingmember has one end adapted to receive a toothbrush handle, and its otherend has a slot formed therein. This slot is formed so that the longerdimension of the slot is greater than the diameter of the path moved bythe pin, and the shorter dimension of the slot is less than the pathdiameter but greater than the pin diameter. rhe pin extends through theslot. Thus, as the motor moves the pin through its circular path, thepin cooperates with the holding member to reciprocate the member. Thehandle also includes a guiding arrangement which permits only straightline reciprocation ot the member in a direction parallel to the casingaxis. The slot is formed so that a line perpendicular to the longiudinalaxis of the slot is positioned at an acute angle with respect to thecasing longitudinal axis. The tangent of this angle is approximatelyequal to the coetiicient of friction between the pin and the Walls ofthe slot. lr the pin moves in a clockwise direction, the angle shouldextend in a clockwise direction from the casing axis. if the pin movesin a countercloclrwise direction, the angle should extendcounterclockwise.

Further features, objects and advantages Will become apparent withreference to the following drawings, in which:

FlG. l is a cross-sectional View of a motorized tooth- SZ'Z atenitedGot. d, 1964 ICC brush handle containing the toothbrush holding memberof the invention;

FIG. 2 is a cross-sectional view of the toothbrush handle rotated fromthe View ot FIG. l and FIG. 3 is an enlarged, cutaway view of a portionof the toothbrush holding member of the invention and the drivin gmechanism of the handle.

ln the cross-sectional views of FlGS. l and 2, there is shown amotorized handle suitable for driving a toothrush. The handle includes atubular casing l@ having a generally cylindrical shape and formed of anupper portion i2 and a lower portion i4. The casing is preferably madeof plastic or similar electrically insulating material which isrelatively strong and lightweight.

In the casing lower portion iid, there is positioned a battery ld fordriving a small direct current motor i8 positioned in upper casingportion t2 and spaced from the battery by an insulating disk Zit. Themotor is controlled by a suitable on-oi' switch mechanism whichincludes, for example, an external control button ZZ which is slidablymounted Within a recess in upper casing portion l2. The button 22. isattached to a Contact member 2d that is slidably moved into or out ofengagement with a pair ot fixed terminals, one of which is shown at 2.3extending through a plate E@ positioned in recess 24. Terminal 2d isconnected by wire 32. to one terminal 34 ofkriotor td as shown in HG. 2.The` other switch terminal is connected by Wire 36 to a terminal S8 ofbattery lid, also seen in FlG. 2. Connecting the other battery terminaltti to the other motor terminal l2 completes the motor battery operatingcircuit.v

in operation, the motor tti produces a rotational output through itsshaft i3 carrying a pinion 5@ and ballast Wheel 52. A member or plunger54 for kholding a toothbrush is shown positioned in the upper end otcasing portion 12. To obtain the straight line reciprocatory motion ofthe holding member 5d, it is necessary that the handle be provided withmotion translating means to translate the motor rotational output intoreciprocal movement in the proper direction and to transmit thismovement to the member 5d and eventually a toothbrush. F or thispurpose, the motor it@ is provided with a mounting bracket 56 attachedto one end of the motor, extending axially within the casing l@ adjacentthe casing inner cylindrical surface. The bracket supports a stub shaft5b carrying a gear adapted to be driven by the pinion di?. A. shaft orpin d2 is secured to dislt @d and eccentrically mounted on gear rlhe pind2 extends in ya direction paraliel to the stub shaft and perpendicularto the longitudinal axis of the casing it?. Thus, the rotational outputof pinion 5b is translated into circular movement of pin 62 in adirection transverse to the pin axis.

To translate the circular motion of pin 62 into axial movement of holder5d, there is provided a uniquely formed slot de in the lower end oftoothbrush holder 54. The slot which extends in a direction primarilytransverse to the longitudinal axis of the casing, as seen in FIG. 2, isadapted to receive a roller d mounted on pin 62 to serve as a bearing-tor the pin. As the motor pinion 5t) rotates, the resulting circularmovement of pin 62 is translated into reciprocal movement of the plunger54 by means of slot ed. Further details concerning the motiontranslating mechanism Will be given in later paragraphs.

It may be seen from FlGS. l and 2 that the holding member is anelongated somewhat cylindrical member having its lower end formed in theshape oi a yoke con prising a pair of diametrical arms 'itl and 72 whichstraddle pin 62 and pinion Sti. The upper end of the holding member isadapted to receive the shank portion oi a toothbrush so that the brushwill move with the holding member. To reduce friction between the member54 and the surrounding casing portion i2, a ball bearing supportarrangement is provided. Each of the arms 7d and 72 is formed with anaxially extending groove 7d and 76, respectively, in the surface facingthe inner wall of casing l2. A pair of complementary grooves 7S and 8@formed in the interior of casing l2 mate respectively with grooves 7dand 76. A ball bearing S2 is positioned within the passage formed bygrooves 7?. and 7o, and ball 3d is similarly positioned` in the grooves76 and To complement the guiding action and stability provided by thebearings and grooves in the lower end of holder 5d, there is provided anadditional pair of grooves S6 and SS diametrically positionedintermediate the ends of the holder. As can be seen from PEG. 2, thisportion of holder 5d has a diameter smaller than the yoke portion sothat the holder will iit within the neck of upper casing portion l2. Apair of grooves 92 and 9d formed within the neck portion 9@ materespectively with holder grooves S6 and Sti, and ball bearings 9d and 9Sare respectively positioned within the passages formed by the matingTgrooves. Thus, it should be appreciated that with the two sets ofgrooves and ball bearings, the holder 5d is smoothly guided forreciprocal straight line movement within the casing lil as it is movedby the eccentrically mounted pin d2.

To prevent moisture and solid particles from entering the toothbrushhandle, there is provided a flexible grommet lill) made of rubber orsimilar material extending between the upper end of holder 54 and theupper end of casing portion l2. T o protect the iingers of the operatorand to prevent interference with the gromrnet lili?, there is providedan annular cap lil?, which tits over the grornmct and surrounds thesocket end of holder 54. The cap is made of plastic or similar materialformed to snap over the casing neck dit and be easily removed forcleaning purposes.

In order to obtain a satisfactory and successful motorized toothbrushhandle, it is of course essential that the handle provide reliableoperation. Also it is extremely important that the handle be lightweightfor easy manipulation. To minimize the weight of the handle, it isdcsirable to minimize the size and weight of the motor and battery, andthis accordingly limits the power output. In order to make maximum useof the motor output it is necessary that the motion translatingmechanism which converts the motor rotational output into reciprocationof the holding member be as eiiicient as possible. In accordance withthe present invention, maximum etliciency and reliability of theeccentric pin and slot arrangement described herein is obtained byuniquely positioning the slot 66 iving due consideration to thedirections of Inovement of the various parts and the frictional forcesinvolved.

Referring to the enlarged view of FIG. 3, it may be seen that the slot66 has an elongated cross-section which may be described as an elongatedoval or elliptical crosssection. For purposes of description, the longerdimension 1M- may be considered the major axis, and the shorterdimension liti@ of the cross-section may be termed the minor axis. Theline lltl may be considered to represent the longitudinal axis of thecasing and the holding member as well as the direction of movement ofthe holding member. Further, the line lil@ intersects the center line ofgear 6@ and is roughly coincident with the center of pinion Sti andmotor shaft d3. lt can be seen that the pin 62 extends through the slotwith the pin center line being substantially perpendicular to the slotcross-section.

The circular path of the pin center line during operation of the motoris shown by the line i12; similarly, the paths of the inner and outersurfaces of the roller et; are shown by the dotted lines lift and M6,respectively. The slot major axis ldd is greater than the diameter ofcircle llld, and the minor axis lilis less than the path diameter lio.

In accordance with the invention, the slot ed within the holder 54 ispositioned such that the minor axis ldd of the slot forms an acute angielid with respect to the line E65 representing the direction of travel ofholder 54- and representing casing longitudinal axis Hi8. The angle il@is shown to be approximately 15 in FIG. 3. HOW- ever, it has been foundthat the most desirable angle iS somewhat dependent upon the materialsemployed for the roller d8 and the holding member 54. More specically,the co-eihcient of friction between these two members has beendiscovered to bear a delinite relation to the optimum angle which shouldbe formed between the minor axis of the cross-section and the lineltlil. It has been found that the optimum angle is roughly that anglewhose tangent is approximately equal to the coefficient of frictionbetween the roller and the holding member. In the case of a bearingbronze roller and a plastic holding member, the coeilicient of frictionis approximately equal to the tangent oi a 15 angle. l

The explanation for the improved results obtained by positioning theslot as described, concerns the force output of the moving pin 62. Asthe pin 62 moves through its circular path, the torce exerted by the pinis represented by a continuously moving line which is tangent to thecircular path described by the pin as it rotates. These forces may ofcourse be analyzed by considering their components in referencedirection such as their horizontal and vertical components. Byconsidering the line lili? as representative of the vertical directionand line llZti as representative of the horizontal direction, it will beappreciated that it is the vertical component of the forces which tendsto move the holding member 5d. Thus, when the pin 62 is positioned asshown in FIG. 3 wherein its axis intersects the line ltltt, the verticalcomponent of the force is zero with all force being directed in thehorizontal direction as indicated by the line Mtb. As the pin is movedthrough a 90 arc the vertical component of the pin force outputincreases from zero to maximum, and then decreases to zero during thenext 90 arc. Thus, it can be seen that the line MZ intersects the linew8 twice during each revolution at which point the vertical force or theforce tending to move the plunger is at zero. For sake of convenience,these two positions may be referred to as the center line, or deadcenter positions. Since it is the vertical resistance to movement of theplunger or holding member 54% which provides the load for the moving pin62 and the vertical force component at dead center is zero, the pintends t0 take one of the center line or dead center positions when themotor is stopped. When the motor is once more started, it is desirablethat the vertical load be at a minimum to permit the pin to move fromthe dead center position sufficiently far so that the Vertical componentof the force exerted by the pin is suiliciently large to overcome theinertia of the member 54. Thus, should the roller stop at its uppermostpoint of travel all of the force resulting from the torque supplied bythe motor upon restarting would be in the horizontal plane or parallelto axis E26, and the inclined slot 66 would permit a vertical forcecomponent to overcome the starting load point to cause member 54 to movein a vertically downward direction toward pinion Sti.

It has been found that if the minor axis of the slot cross-section isformed coincident with the direction of travel represented by line 1.68substantial force would be required to move the pin from the dead centerposition if it had stopped in such position. During each revolution ofthe pin, there will be two areas which might be termed minimumresistance or minimum load zones regardless of the angular position ofthe slot. These zones exist where the pin major axis 104 is roughlyparallel to the direction of movement of the pin. Technically speaking,this occurs at only two points; however, as a practical matter, theareas on each side of these points for a short angular distance may beconsidered as minimum load zones. By positioning the slot so that thepin 62 is just entering the zone of minimum resistance to movement whenit is at the dead center position, reliable starting operations may beobtained. It will be appreciated that the minimum resistance or loadzone may be considered to vary depending upon the coefficient offriction of the sliding components.

From the foregoing description, it will be appreciated that the angle118 formed by the minor axis 106 and the direction of travel indicatedby the line 108 bears a definite relation to the direction of movementof pin 62. When the pin is moved in a clockwise direction, as in'-dicated by arrow 122, in FIG. 3, the slot 66 should be positioned sothat the angle is positioned in a clockwise direction with respect tothe line 108. If the pin were to be moved in a counterclockwisedirection, the angle 118 should extend in a counterclockwise directionfrom the 'tine 108. Stated in other words, the line 108 marks thebeginning of the minimum load zone, and the angle 118 should angularlyextend in the circular direction of movement of the pin. Further, itmight be said that the outer surface of the pin enters the angled areaby intersecting the side of the angle defined by the casing axis.

From the foregoing description, it will be appreciated that a smoothlyoperating motion translating mechanism for a motorized toothbrush handlehas been described and that the arrangement is particularly advantageousfor insuring reliable starting operation. While a specic em bodiment ofthe invention has been shown and described, it should be understood thatthe invention is not limited to the particular construction disclosed.Accordingly, it is intended in the appended claims to cover allmodications within the true spirit and scope of the invention.

Having thus described the invention, what is claimed is:

1. In a motorized handle for driving a toothbrush, a casing having alongitudinal axis, a holding member positioned Within one end of saidcasing, said member having one end adapted to receive a toothbrush, amotor positioned in said casing, rotary means driven by said motor, apin extending in a direction substantially perpendicular to said casinglongitudinal axis, said pin being mounted on said rotary means to bemoved in a circular path by said motor in a direction transverse to thepin axis, an elongated slot extending through the opposite end of saidholding member having a major and a minor axis, the major axis of theslot being greater than the diameter of the path moved by said pin, theminor axis of the slot being less than the path diameter but greaterthan the pin diameter, said pin and slot being arranged so that the pinextends through the slot in a direction perpendicular to thelongitudinal axis of the slot whereby circular movement of said pinreciprocates said holding member, guide means permitting only straightline reciprocation of said member in a direction parallel to the casinglongitudinal axis, the minor axis of the slot being located with respectto said holder direction of travel at an acute angle whose tangent isapproximately equal to the coeicient of friction between said pin andsaid slot, the rotational direction of said pin being the same as theangular direction said angle extends from the holder direction oftravel.

2. In a motorized handle for driving a toothbrush, a tubular casinghaving a longitudinal axis, a toothbrush holder member positioned in oneend of said casing, said member having one end adapted to receive atoothbrush handle, a motor positioned in said casing, rotary meansdriven by said motor, a driving pin eccentrically mounted on said rotarymeans to be moved in a circular path in a direction transverse to thepin axis, a slot extending through the opposite end of said holdingmember having substantially an elongated oval or elliptical shape with amajor and a minor axis, the major axis of the slot being greater thanthe diameter of the path moved by said pin, the minor axis of the slotbeing less than the path diameter but greater than the pin diameter,said pin extending in a direction substantially perpendicular to saidcasing longitudinal axis and extending through the slot, guide meanspermitting only straight line reciprocation of said member in adirection parallel to the casing longitudinal axis, the minor axis ofthe slot being located with respect to said casing longitudinal axis atan acute angle in the range between 10 and 20.

3. A motorized toothbrush handle comprising a casing having alongitudinal axis, a toothbrush holding member positioned within one endof said casing, said member having one end adapted to receive atoothbrush, a battery positioned in the opposite end of said handle, amotor positioned adjacent said battery and driven by the battery, rotarymeans driven by said motor, a cylindrical pin extending in a directionsubstantially perpendicular to said casing longitudinal axis, said pinbeing eccentrically mounted on said rotary means to be moved in acircular path by said motor in a direction transverse to the pin axis, aslot extending through the opposite end of said holding member having amajor and a minor axis, said pin and siot being arranged so that the pinextends through the slot, the major and minor dimensions of said slotbeing of such size with respect to the circular path of said pin thatthe pin circular movement reciprocates said holding member, guide meanspermitting only straight line reciprocation of said member in adirection parallel to the casing longitudinal axis, said pin being movedthrough two zones of minimum load in the two portions of its circularpath wherein the slot major axis is roughly parallel to the direction ofmovement said pin, said slot minor axis forming an acute angle withrespect to said casing axis such that said pin will reach points ofminimum load in said zones of minimum load after crossing said casingaxis.

4. A motorized toothbrush handle comprising a tubular casing having alongitudinal axis, a member slidably mounted for reciprocation withinsaid casing, a motor positioned in said casing, rotary means driven bysaid motor, a driving shaft eccentrically mounted on said rotary meansto be moved in a circular path in a direction transverse to the shaftaxis, a slot extending through one end of said member and having anelongated oval crosssection with a major and a minor axis, the majoraxis being greater than the diameter of the path of said shaft, theminor axis being less than the path diameter but greater than the shaftdiameter, said shaft and slot being arranged such that the shaft extendsthrough the slot so that circular movement of said shaft reciprocatessaid member, the minor axis of the slot being positioned with respect tosaid casing axis at an acute angle whose tangent is approximately equalto the coecient of friction between said shaft and said slot, said anglebeing located clockwise from the casing axis if said shaft is to bemoved in a clockwise direction and located counterclockwise from theaxis when the shaft is to be moved in a counterclockwise direction.

5. In a motorized toothbrush handle, a casing having a longitudinalaxis, a plastic toothbrush holding member positioned within one end ofsaid casing, said member having one end adapted to receive a toothbrushhandle, a motor, positioned in said casing, rotary means driven by saidmotor, a cylindrical pin extending in a direction substantiallyperpendicular to said casing longitudinal axis, said pin being mountedon said rotary means to be moved in a circular path by said motor in adirection transverse to the pin axis, a steel roller bearing mounted onsaid pin, a slot extending through the opposite end of said holdingmember having substantially an elongated oval cross-section with a majorand a minor axis, the major axis being greater than the diameter of thepath 7 C moved by said pin and roller bearing, the minor axis tionbetween said roller and the Walls defining said slot, being less thanthe path diameter but greater than the said angle being positioned inthe same angular direction roller bearing diameter, said pin and slotbeing arranged from said casing axis as the rotational direction of saidso that the pin extends through the slot in a direction pm.

perpendicular to the slot cross-section so that the circular 5 movementof said pin reciprocates said holding member, References Cmd 1n the fue0f this Patent guie mealrjis permiti'ng only strailglhltinerleciprocatilon of UNITED STATES PATENTS sai mem er m a irec ionpara e o e casing ongitudinal axis, the minor axis being positioned withrespect Sgleschmldt plr' to said casing longitudinal axis at an acuteangle Whose 10 3064583 Burt Nu y 20 1962 tangent is approximately equalto the coeicient of fric- 0V'

1. IN A MOTORIZED HANDLE FOR DRIVING A TOOTHBRUSH, A CASING HAVING ALONGITUDINAL AXIS, A HOLDING MEMBER POSITIONED WITHIN ONE END OF SAIDCASING, SAID MEMBER HAVING ONE END ADAPTED TO RECEIVE A TOOTHBRUSH, AMOTOR POSITIONED IN SAID CASING, ROTARY MEANS DRIVEN BY SAID MOTOR, APIN EXTENDING IN A DIRECTION SUBSTANTIALLY PERPENDICULAR TO SAID CASINGLONGITUDINAL AXIS, SAID PIN BEING MOUNTED ON SAID ROTARY MEANS TO BEMOVED IN A CIRCULAR PATH BY SAID MOTOR IN A DIRECTION TRANSVERSE TO THEPIN AXIS, AN ELONGATED SLOT EXTENDING THROUGH THE OPPOSITE END OF SAIDHOLDING MEMBER HAVING A MAJOR AND A MINOR AXIS, THE MAJOR AXIS OF THESLOT BEING GREATER THAN THE DIAMETER OF THE PATH MOVED BY SAID PIN, THEMINOR AXIS OF THE SLOT BEING LESS THAN THE PATH DIAMETER BUT GREATERTHAN THE PIN DIAMETER, SAID PIN AND SLOT BEING ARRANGED SO THAT THE PINEXTENDS THROUGH THE SLOT IN A DIRECTION PERPENDICULAR TO THELONGITUDINAL AXIS OF THE SLOT WHEREBY CIRCULAR MOVEMENT OF SAID PINRECIPROCATES SAID HOLDING MEMBER, GUIDE MEANS PERMITTING ONLY STRAIGHTLINE RECIPROCATION OF SAID MEMBER IN A DIRECTION PARALLEL TO THE CASINGLONGITUDINAL AXIS, THE MINOR AXIS OF THE SLOT BEING LOCATED WITH RESPECTTO SAID HOLDER DIRECTION OF TRAVEL AT AN ACUTE ANGLE WHOSE TANGENT ISAPPROXIMATELY EQUAL TO THE COEFFICIENT OF FRICTION BETWEEN SAID PIN ANDSAID SLOT, THE ROTATIONAL DIRECTION OF SAID PIN BEING THE SAME AS THEANGULAR DIRECTION SAID ANGLE EXTENDS FROM THE HOLDER DIRECTION OFTRAVEL.